Extensive work has been performed during the last ten years to build and investigate photonic crystals, the optical analogues to electronic semiconductors. Photonic crystals are materials built to present a periodic variation of refractive index. The periodicity being the same order of magnitude as the wavelength of the electromagnetic (EM) waves, these structures exhibit band gaps for photons. The propagation of the EM waves can be controlled by changing the periodicity and introducing point or line defects in the photonic crystal. A. Birner et al in, xe2x80x9cSilicon-based photonic crystals,xe2x80x9d Adv. Mater. 13, 377-388 (2001), recently reviewed 1D, 2D, and 3D photonic crystals made out of silicon.
Foresi et al in, xe2x80x9cPhotonic-bandgap microcavities in optical waveguides,xe2x80x9d Nature 390, 143-145 (1997), and Birner et al in, xe2x80x9cTransmission of microcavity structure in a two-dimentional photonic crystal based on macroporous silicon,xe2x80x9d Materials Science in Semiconductor Processing 3, 487-491 (2000), disclose that 1D and 2D structures, respectively, are usually built by drilling well-controlled pores in a silicon wafer by electrochemical etch or by electron beam lithography. In, xe2x80x9cLarge-scale synthesis of a silicon photonic crystal with a complete three-dimensional bandgap near 1.4 micrometer,xe2x80x9d Nature 405, 437-440 (2000), Blanco et al disclose that 3D structures usually involve the growth of a crystal by chemical vacuum deposition on a periodic template followed by the dissolution of the template (inverse opal structure).
An aspect of the invention includes a photonic waveguiding device comprising: at least one silicon wafer having a plurality of through pores distributed according to a designed pattern leading to a photonic band gap; and at least one chemical or biological target specific anchor attached to the inner wall of at least one of the pores, wherein the anchor is capable of binding to a specific chemical or biological target molecule.
Another aspect of the invention includes a photonic waveguiding device comprising: an array of waveguiding filters, wherein each filter is functionalized with a chemical or biological target specific anchor to allow the contemporaneous detection of various chemical and biological target molecules and wherein each of the filters comprise (1) a silicon wafer having a plurality of through pores distributed according to a designed pattern leading to a photonic band gap and (2) a chemical or biological target specific anchor attached to the inner wall of at least one of the pores, the anchor being capable of binding to a chemical or biological target molecule.
A further aspect of the invention includes a photonic waveguiding detection system comprising: a light source; at least one silicon waveguiding filter, wherein the filter comprises a silicon wafer having (1) a plurality of through pores distributed according to a designed pattern leading to a photonic band gap and (2) at least one chemical or biological target specific anchor attached to the inner wall of at least one of the pores, wherein the anchor is capable of binding to a chemical or biological target molecule; a detector to count the photons transmitted through the device; and a computer to analyze the light transmitted through the filter by (1) recording the intensity and wavelength of light transmitted through the filter, (2) identifying the presence of target molecules bound in the device and (3) determining the concentration of bound target molecules.
A further aspect of the invention includes a method comprising:
measuring the transmission curve through at least one silicon filtering device, wherein the filtering device comprises (1) a plurality of through pores distributed according to a designed pattern leading to a photonic band gap and (2) at least one chemical or biological target specific anchor attached to the inner wall of at least one of the pores, wherein the anchor is capable of binding to a chemical or biological target molecule; passing a sample through the silicon filter, the sample being a gas or a liquid; shining a light orthogonal to the pores of the silicon filter, while contemporaneously flowing the sample through the filter; and measuring the transmission curve of the waveguiding silicon filter as the sample passes through the filter, wherein modifications in the transmission curve are (1) indicative that at least one of the target molecules has bound to the anchor and (2) indicative of the concentration of the bound target molecules.
Another aspect of the invention includes a method comprising:
fabricating a silicon membrane with an array of pores designed for opening a photonic band gap and for waveguiding; functionalizing the pore walls of the silicon membrane with chemical functional groups; and attaching biological or chemical anchors to the functionalized walls of the membrane to create a selective silicon photonic waveguiding filter.